By way of example, Wireless Local Area Network (WLAN) and Bluetooth™ transceivers may share a common receiver communications path when located at essentially the same place, which is typically referred to as collocation. It is desirable that in a system including collocated WLAN and Bluetooth™ receivers, as much of the radio frequency front end be shared, in particular an antenna and a Low Noise Amplifier (LNA) with possibly a mixer and low pass filter providing a baseband signal to the LNA.
Such systems may have a problem regarding the gain of an LNA that may be shared to amplify the incoming radio signals from an antenna. The gain of the LNA needs to be set to amplify the weakest Radio Frequency (RF) signal for these transceivers while not over amplifying the stronger signal(s). Alternatively, some prior art systems split the signal path in front of two LNA's, one for each receiver. This approach has the disadvantage of reducing the signal sensitivity, possibly by as much as three decibels (db).
Once one transceiver is receiving data, the gain cannot change without potentially corrupting the reception of the frame or packet for that transceiver. Often, one transceiver starts receiving a frame and setting the LNA gain. The second transceiver starts receiving a packet while the first reception is still going on. If the LNA gain is set too low, the second reception may be corrupted. If the LNA gain is set too high, the amplification of the second signal may be too large and the LNA may be driven into a non-linear region of response and the reception of the second frame may be corrupted. To simply this disclosure but not limit the scope of the claims the unit of reception for relevant communications protocols will be referred to as a packet.
Several attempts to solve this problem have been considered. While a LNA with a wider dynamic range can be used, such amplifiers require greater power, which increases the power consumption of the corresponding system all the time to solve a problem that typically only shows up some of the time. Another approach sets the gain of the LNA to provide one of the two circuits with the average Received Signal Strength Indication (RSSI) and provide the other circuit with a gain that provides a stronger signal. This approach has the problem that Bluetooth™ can maintain an RF link to multiple physical links at once, each with its own RSSI, possibly making the use of average RSSI insufficient. Methods and apparatus are needed that support control of the LNA gain to concurrently support reception of both WLAN and Bluetooth™ signals.